Industrial slings are designed to lift, transport and move extremely heavy loads. Thirty years ago, the vast majority of industrial slings were made of metal (either chains or wire rope). More recently, non-metal or synthetic slings have gained popularity and are replacing metal slings in many circumstances.
Synthetic slings are usually comprised of a lifting core made of twisted strands of synthetic fiber and an outer cover that protects the core. The outer cover plays an important role in synthetic slings. The cover is designed to move with respect to the inner core in order to reduce the likelihood of wear points. Also, the outer cover provides a means for protecting the inner core from the elements (e.g., heat, cold, chemicals, etc.). Therefore, once the cover is damaged the probability that the load-bearing inner core will be exposed and damaged increases dramatically.
When a metal sling was used to lift an abrasive load/object (e.g., one made of concrete) or any object having a sharp edge, there was little concern that the metal sling would be damaged. However, with the advent of synthetic slings, the damage that may be done to the outer cover by an abrasive or sharp object is of particular concern. The size and/or shape of the load/object may require that the sling be placed next to an abrasive surface or, more commonly, against an edge (e.g., an elongated stretch where two pieces of metal are joined to form a 90° angle) of the load to be lifted. The tremendous force applied to the sling at the point of contact with the load being lifted may damage the sling.
Some large objects that have particularly sharp edges or which are particularly unwieldy undergo the additional manufacturing step of attaching ring bolts, eye bolts or lifting loops in order to accommodate the slings needed to move the objects. If the object being lifted is made of metal, the eye bolts are attached by welding ring-shaped pieces to the object. For example, large pipe sections, cargo ship sections, structural steel for a sky scraper or bridge section may be manufactured with multiple eye bolts.
It should be noted that the eye bolts cannot be placed just anywhere on the object to be lifted. The eye bolts must be placed at points accessible by the slings, so that during a lift the load is stable. In addition, the load must be properly oriented once it is lifted or moved into position. Specifically, the eye bolts must take into consideration the center-of-gravity of the object so that the object does not drop into an odd position or begin to spin uncontrollably as it is being lifted.
Once the object is moved to its final destination and placed in its permanent position, the eye bolts may be removed from the object by cutting, burning or unwelding. Clearly, the extra steps of calculating the object's center-of-gravity, attaching the plurality of eye bolts in an appropriate location and then removing the eye bolts after the object has reached its final destination increases the time and cost of a lifting operation. Moreover, if the load is not made of iron it is much more difficult to attach eye bolts.
For shipping purposes, it is known to manufacture protectors by forming angular pieces of cardboard to abut against various goods/objects. Also, foam inserts that are custom designed to fit against the edge of a particular object serve a similar purpose. The protectors are designed to absorb some of the force to which the object will be exposed during normal shipping and handling. For example, televisions, filing cabinets, furniture, computers, washers, refrigerators and similar appliances are shipped inside cardboard boxes, with protectors placed along several edges, thereby providing a measure of protection. These types of protectors are designed to protect the object during shipping and handling. As long as the goods are protected, the destruction of the cardboard boxes and the foam protectors are irrelevant since they are disposed of once the goods are unpacked.
U.S. Pat. No. 6,470,637 to Jeffrey Gratz discloses a corner protector made of molded pulp that protects goods/objects such as windows during shipments. The corner protector disclosed in U.S. Pat. No. 6,470,637 is inexpensive to manufacture. Since it is disposed of once the window reaches its destination and is unpacked, the corner protector disclosed in U.S. Pat. No. 6,470,637 is designed to be biodegradable.
The aforementioned cardboard and foam protectors are specifically designed and shaped to protect the contents (i.e., the object being shipped or moved). They are not designed to protect the means used to lift the object (e.g., a sling, rope, fork-lift, overhead crane, etc.). Furthermore, the cardboard and foam protectors would provide negligible protection when used under the conditions in which industrial slings are used. Accordingly, there is a need in the industry to develop an apparatus that could be quickly and safely (and preferably releasably) secured to an industrial sling, lifting or towing chains, wire rope, etc. that would protect the sling, towing chain, wire rope, etc. from abrasive or sharp edges at the points where the sling contacts its load.